Carbs, and not saturated fat, raise blood lipid levels: New evidence

Saturated fats have always been looked at as a dietary demon implicated to cause a host of lifestyle diseases. Recently, results of a new American study have challenged this conventional wisdom.

The study found that increased consumption of saturated fat did not increase the saturated fat levels in the blood. However, increased consumption of carbohydrates in the diet was associated with an increase in the level of palmitoleic acid, a fatty acid associated with diabetes and heart disease. These results were published in the PLOS ONE journal.

The researchers recruited 16 adults, each of whom had metabolic syndrome. Before commencement of the study, the researchers spent 3 weeks to get the participants to a baseline reduced carb diet. They were then given six 3-week diets each containing 2,500 calories and around 130 grams of protein. The first diet consisted of 47 g of carbohydrates and 84 g of saturated fat daily. Subsequently, the carb-saturated fat ratio was increased such that the final diet had 346 g of carbs and 32 g of saturated fat daily. The final diet provided 55% of daily calories from carbohydrates which is akin to the typical American diet.

• Interestingly, among those on the high-fat/low-carb diets, the levels of the incriminating palmitoleic acid was lower, whereas in the high carb/low fat diet group, the levels of this acid increased as the carbohydrate content of the diet rose during the day.

To corroborate this result, the researchers fed a small number of participants with diets in the reverse order that is starting with the high carb diet first. They found a similar increase in the level of palmitoleic acid.

According to the researchers, an increase in the palmitoleic acid levels indicates that carbohydrates are being converted to fats instead of being burnt as fuel. Conversely, increasing dietary fat and reducing carbohydrates could ensure that the body uses saturated fat for fuel instead of storing it in the body. They also found that individual tolerances to carbohydrates dictate when the fat starts getting stored while on a high carb diet.

Talking about the study and the much known association of saturated fat with diseases, lead researcher Prof. Volek said, “Studies measuring saturated fat in the blood and risk for heart disease show that there is an association. Having a lot of saturated fat in your body is not a good thing. The question is, what causes people to store more saturated fat in the blood, or membranes or tissues?”